This invention relates to insulated chimney piping and to methods of connecting the same to form piping for a chimney. More specifically, the invention relates to a positive pressure coupling for a vent pipe, to a vent pipe incorporating the same and to a method of forming vent piping by coupling together such vent pipes. Chimney vent pipes include an inner pipe casing within an outer pipe casing and include an insulating material there-between so as to insulate the outer pipe casing from the heat generated by the gases being vented through the inner pipe casing. In this regard, the outer pipe casing stays cooler than the inner pipe casing, preventing the heat from being transferred to the surrounding structure of the chimney which may lead to hazards, such as fires. Typically, chimney vent piping is formed by coupling together multiple vent pipes. Each vent pipe 10 includes an inner pipe casing 12, an outer pipe casing 14 and an insulating material 16 there-between, as for example shown in FIGS. 1 and 2. The inner pipe casing of each pipe is formed such that it is longer than the outer pipe casing such that a portion 18 of the inner pipe casing extends beyond the outer pipe casing. A flange 20 is formed at the end of the inner pipe casing extending radially outwards. To connect the two pipes together, a sealant is placed on the flange 20 of the inner pipe casing of the first pipe, as well as a flange 20 of an inner pipe casing of a second pipe, as for example shown in FIG. 2. The two pipes are brought together such that the flange 20 of the first pipe sits on the flange 20 of the second pipe, as for example shown in FIG. 3. A gasket material may also be used between the two flanges. The sealant and/or the gasket material typically needs to be capable of withstanding 2,000° F. Not many materials can withstand such temperatures. An annular inner V-band 22, as shown in FIG. 1, is placed over the mated flanges 20. The V-band 22 is an annular band section defining a “V” in cross-section, as for example shown in FIG. 1, such that it can fit over the mated flanges 20. The V-band is formed in sections such that it can be put together to surround the mated flanges of the two inner pipe casings. A sealant is also placed in the inner surface 24 of the V-band, which is placed over the mated flanges 20. Once the sections of the V-band are in place, they are clamped together so as to tightly clamp on to the inner pipe casings. Insulating material 26 is then placed over the V-band between the outer pipe casings of the two pipes being connected. Once the insulating material is fitted properly, an outer channel band 30 is then used to connect the two outer pipe casings 14 by clamping on to the two outer pipe casings 14. The outer band has circumferential flanges 32 formed on its edges which fit in annular groves 34 formed on the outer pipe casings. The coupling of vent pipes according to the prior art is described in U.S. Pat. No. 3,902,744. As can be seen, the connection of prior vent pipes is a cumbersome process that takes time, especially if multiple pipes need to be connected together, and also requires sealants and/or gaskets that can withstand high temperatures, as for example 2,000° F. As such, vent pipes are desired that can be easily coupled to each other and that can be coupled to each other without the use of high temperature adhesives, sealants or gaskets.